The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
In the natural lens, bifocality of distance and near vision is provided by a mechanism known as accommodation. The natural lens is contained within the capsular bag and is soft early in life. The bag is suspended from the ciliary muscle by the zonules. Relaxation of the ciliary muscle tightens the zonules, and stretches the capsular bag. As a result, the natural lens tends to flatten. Tightening of the ciliary muscle relaxes the tension on the zonules, allowing the capsular bag and the natural lens to assume a more rounded shape. In this way, the natural lens can focus alternatively on near and far objects.
As the lens ages, it becomes harder and is less able to change its shape in reaction to the tightening of the ciliary muscle. This makes it harder for the lens to focus on near objects, a medical condition known as presbyopia. Presbyopia affects nearly all adults over the age of 45 or 50.
When age or disease causes the crystalline lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and ultrasonically vibrated. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens. Implantation of conventional IOLs may restore vision in cataract patients, but cannot alleviate presbyopia.
Extensive research efforts have been contributed to develop accommodating IOLs which could have the capability to either change its optical power as the natural crystalline lens in response to contraction of the cilliary muscle. One of the active research areas for accommodating IOLs is fluid-based accommodating IOLs that can undergo curvature change upon contraction/relaxation of cilliary muscle (e.g., U.S. Pat. Nos. 4,787,903, 4,816,031, 4,932,966, 5,066,301, 5,443,506, 6,117,171, 6,730,123, 7,122,053, 7,217,288, 7,247,168, 7,261,737, 7,438,723, 7,485,144, 7,753,953, 7,776,088, 8,038,711, 8,048,155, 8,158,712, 8,197,541, 8,361,145, 8,398,709, 8,454,688, 8,475,529, and U.S. patent application publication No. 2013/02668070 A1, herein incorporated by reference in their entireties). U.S. Pat. No. 8,158,712 described biocompatible polymers which comprise trifluoroethyl methacrylate (or its alternative), butyl acrylate (or its alternative), and phenyl ethylacrylate (or its alternative), and have a modulus of elasticity between about 0.1 MPa and about 0.6 MPa and a refractive index between about 1.44 and about 1.52, and is substantially resistant to the diffusion of fluid, such as silicone oil, water or saline. According to U.S. Pat. No. 8,158,712, those biocompatible polymers may be useful for making accommodating IOLs, which comprise a deformable optics front surfaces and soft deformable haptics that rely on fluid driving changes in the shape of the deformable optics's front surface.